arXiv subjects

Stephen H. Shenker

Publications and source records attributed to Stephen H. Shenker.

21 records · Page 2Linked to original sources

arXiv1996

D-branes and Short Distances in String Theory

We study the behavior of D-branes at distances far shorter than the string length scale~$l_s$. We argue that short-distance phenomena are described by the IR behavior of the D-brane world-volume quantum theory. This description is valid until the brane motion becomes relativistic. At weak string coupling $\gs$ this corresponds to momenta and energies far above string scale. We use 0-brane quantum mechanics to study 0-brane collisions and find structure at length scales corresponding to the eleven-dimensional Planck length ($\lp11 \sim \gs^{1/3} l_s$) and to the radius of the eleventh dimension in M-theory ($\R11 \sim \gs l_s$). We use 0-branes to probe non-trivial geometries and topologies at sub-stringy scales. We study the 0-brane 4-brane system, calculating the 0-brane moduli space metric, and find the bound state at threshold, which has characteristic size $\lp11$. We examine the blowup of an orbifold and are able to resolve the resulting $S^2$ down to size $\lp11$. A 0-brane with momentum approaching $1/\R11$ is able to explore a larger configuration space in which the blowup is embedded. Analogous phenomena occur for small instantons. We finally turn to 1-branes and calculate the size of a bound state to be $\sim \gs^{1/2} l_s$, the 1-brane tension scale.

hep-th↗

arXiv1995

Another Length Scale in String Theory?

We suggest that some of the remarkable results on stringy dynamics which have been found recently indicate the existence of another dynamical length scale in string theory that, at weak coupling, is much shorter than the string scale. This additional scale corresponds to a mass $\sim m_{\rm s}/g_{\rm s}$ where $m_{\rm s}$ is the square root of the string tension and $g_{\rm s}$ is the string coupling constant. In four dimensions this coincides with the Planck mass.

hep-th↗

arXiv1995

Dynamics of $SU(N)$ Supersymmetric Gauge Theory

We study the physics of the Seiberg-Witten and Argyres-Faraggi-Klemm-Lerche-Theisen-Yankielowicz solutions of $D=4$, $\mathcal{N}=2$ and $\mathcal{N}=1$ $SU(N)$ supersymmetric gauge theory. The $\mathcal{N}=1$ theory is confining and its effective Lagrangian is a spontaneously broken $U(1)^{N-1}$ abelian gauge theory. We identify some features of its physics which see this internal structure, including a spectrum of different string tensions. We discuss the limit $N\rightarrow\infty$, identify a scaling regime in which instanton and monopole effects survive, and give exact results for the crossover from weak to strong coupling along a scaling trajectory. We find a large hierarchy of mass scales in the scaling regime, including very light $W$ bosons, and the absence of weak coupling. The light $W$'s leave a novel imprint on the effective dual magnetic theory. The effective Lagrangian appears to be inadequate to understand the conventional large $N$ limit of the confining $\mathcal{N}=1$ theory.

hep-th↗